Motor controllers govern the operation of a motor in order to direct activation, speed, torque, motor shaft position and other such characteristics of the motor during operation. Alternating current (AC) variable speed (motor) drives (VSD) may have encoderless feedback for control of the motor. Encoderless speed controls or estimators are based on the principle that the motor speed can be estimated from a measurement of the current or voltage waveform at a motor connection. Motor rotation induces other frequencies in the current waveform due to the physical construction (rotor bars or winding gaps) of the motor's rotor. A speed estimate can be generated by detecting these induced speed related frequencies and comparing them to known mathematical models relating the induced frequencies to the motor speed. Such a known mathematical model may be, for example, “The Nature of Induction Machines”, P. Alger; Gordon and Breach, New York, 1965.